1. Field of the Invention
The field of the invention relates to a fastener and a tool for driving the fastener, and more particularly to a screw fastener with a head having a configuration which is engagable with a driving tool having an element shaped complementary to the fastener head to interlock with it and thus drive the screw.
2. Description of the Prior Art
Many screw fastener and screwdriver combinations having complementary shaped engaging or driving elements are known in the prior art. Some of the most common types of screw fasteners presently in use are the slotted, "Allen", "Phillips", and "Torx" head screws. However, the head configurations of these prior art screw fasteners are all subject to rounding and distortion of their driving surfaces and corners due to the axial pressure and high torque applied to them by the screwdriver during their engagement, causing slippage and disengagement of the fastener and the screwdriver. Accordingly, once the driving means of the fastener head becomes distorted, it cannot be driven in either direction, which thus requires a time consuming and costly removal procedure such as drilling which can be particularly difficult when using hardened fasteners, since such fasteners may require the use of tungsten carbide drills to be removed.
Various fastener and driving tool combinations have been utilized in the prior art. For example, U.S. Pat. No. 4,311,071 to Bassil sets forth a screwdriver and screw system wherein the screw head is provided with a driving configuration comprising a pair of opposed protruding sectors, each sector having a pair of setback or undercut side walls, said sectors protruding from a flat top surface. A screwdriver has a driving blade having a pair of opposed, outwardly slanted side walls which are selectively engagable with one side wall of each opposing sector when the screwdriver is placed in either of two diametral positions.
U.S. Pat. No. 4,526,071 to Post illustrates another screwdriver and screw fastener combination comprising a screw having a driving head provided with a diametral and a chordal slot. A screwdriver has a driving blade with a laterally extending bit shaped for reception into the chordal slot, and a narrow tip portion on the blade end adjacent to the bit which is positionable in the diametral slot to effect turning of the fastener. Further, a spring clip is provided to retain the screwdriver and fastener in engagement during turning.
U.S. Pat. No. 4,590,825 to Vaughn discloses another screw fastener and driving tool arrangement wherein the frusto-conical head of the screw is provided with a bow-tie shaped driving slot in its driving face. A conical recess is positioned centrally in the driving slot. A driving tool is provided with a driving tip on its end which is shaped complementary to the screw head driving slot to effect centered engagement of the screw and the tool for subsequent driving of the screw.
U.S. Pat. No. 4,858,504 to Tsai discloses a screwdriver having an insulated handle, an insulated block, and a polygonal wrench-engaging head mounted on one end of its shank whereby the screwdriver may be either driven by turning the handle or by attaching another manual or power tool to the head. The insulated handle and block protect an operator from electrical shock. Further, the screwdriver may be used with a hammer as a chisel device to loosen fasteners.
U.S. Pat. No. 4,936,172 to Jackson illustrates still another combination screw and screwdriver wherein the screw is constructed with a slotted driving head for receiving a screwdriver having a drive tip configured with a shape complementary to the head slot. The mating head slots and driver tips are basically rectangular with a plurality of angular contacting wall surfaces.
As such, it may be appreciated that there continues to be a need for a new and improved screw fasteners and driving tools which addresses both the problems of ease of use, portability, and effectiveness in construction, and in this respect, the present invention fulfills this need.